#315 Renamed all files to snake_case (#993)

graphs/bfs.py

@@ -0,0 +1,41 @@
+"""
+BFS.
+
+pseudo-code:
+
+BFS(graph G, start vertex s):
+// all nodes initially unexplored
+mark s as explored
+let Q = queue data structure, initialized with s
+while Q is non-empty:
+    remove the first node of Q, call it v
+    for each edge(v, w):  // for w in graph[v]
+        if w unexplored:
+            mark w as explored
+            add w to Q (at the end)
+
+"""
+
+import collections
+
+
+def bfs(graph, start):
+    explored, queue = set(), [start]  # collections.deque([start])
+    explored.add(start)
+    while queue:
+        v = queue.pop(0)  # queue.popleft()
+        for w in graph[v]:
+            if w not in explored:
+                explored.add(w)
+                queue.append(w)
+    return explored
+
+
+G = {'A': ['B', 'C'],
+     'B': ['A', 'D', 'E'],
+     'C': ['A', 'F'],
+     'D': ['B'],
+     'E': ['B', 'F'],
+     'F': ['C', 'E']}
+
+print(bfs(G, 'A'))